1. Field of the Invention
The invention relates to an isolation structure and a semiconductor device and a manufacturing method thereof, and more particularly, to an isolation structure integrated with a semiconductor device and a manufacturing method.
2. Description of the Prior Art
In recent years, along with the trend for achieving higher packing density in integrated circuit semiconductor devices, active research and development have been in progress, striving for device miniaturization. Furthermore, isolation regions, which are necessary to prevent current short between devices, taking up a considerable portion of a chip, is become more and more important due to the device miniaturization.
Conventionally, the LOCOS (local oxidation of silicon) method has been generally utilized as one of the techniques for forming isolation regions on a substrate. And the conventional process for forming an isolation structure by the LOCOS method is to form a pad oxide layer over a silicon substrate, and a hard mask is then formed thereon. The hard mask and the pad oxide layer are patterned to define location and size of the isolation structure(s) to be formed. Next, the silicon substrate is placed in a high temperature environment with reaction gas such as oxygen, and an oxidation is performed to form field oxide (hereinafter abbreviated as FOX) layers. The FOX layers are used to define active regions on the silicon substrate and to provide electrical isolation between those active regions.
Although FOX layers presently provide many advantages in semiconductor technology, there are still several problems created by their application to a ULSI circuit die, including “birds' beak” effect. The “bird's beak” effect results from the lateral oxidation under edge of the patterned mask and pad oxide layer. The presence of the bird's beak effectively increases the size of the FOX layers, thereby ultimately decreasing the amount of silicon real estate available for later device formation. Furthermore, since LOCOS method needs high temperature, time for performing LOCOS method or forming the FOX layers must be at the beginning of the whole manufacturing steps, otherwise devices formed on the substrate are severely impacted.
Therefore, an isolation structure that is able to provide sufficient electrical isolation, avoid birds' beak effect, and reduce silicon consumption is still in need.